Though the law applies only to cars sold in California, it will force the manufacturers to develop fuel-efficient technologies that all cars can use.

Some are now touting plug-in hybrid cars as the next step in fuel-efficient technology.

These savings would be just the beginning, because higher prices would also intensify the race to bring new fuel-efficient technologies to market.

Still on the table as part of the energy bill are tax credits for consumers who buy vehicles that use fuel-efficient technologies like hybrid gas-electric engines.

Developing, fabricating, and testing two system-level demonstrators that incorporate fuel-efficient technologies.

"Today's autos are 99 percent cleaner than a generation ago, and every model of auto is now available with some type of fuel-efficient technology."

And its advanced low-emission, fuel-efficient technologies also make its products increasingly eco-friendly.

Proponents say that less severe steps are likely, like requiring automakers to make improvements by using more fuel-efficient technologies or measures to expand public transportation.

Due to its limited fuel capacity, the Aurora will rely on advanced fuel-efficient technologies for propulsion.

Toyota and Honda have both aggressively pursued more fuel-efficient technologies as regulations tighten around the world.